Formulation development of cream incorporating extracts of <em>Glycyrrhiza glabra</em> (Licorice)

Abstract

Purpose : Creams are semisolid preparations that can be either oil in water or water in oil type and are usually medicated and intended for external application. Present study describes the formulation development and characterization of cream using Glycyrrhiza glabra (licorice) with the intension of developing a cream with whitening effect. Methods : Two stable bases (formulation 1[F1] and formulation 2[F2]) with different ratios of virgin coconut oil (F1-41.2% and F2- 48.6%), Tween 80 (F1-22.3% and F2-24.3%), and distilled water (F1-36.5% and F2-27.1%) were identified based on previous research done at our laboratory and their stability was studied. Methanolic licorice extract in five different concentrations (1-5% w/w) were incorporated into the selected cream bases. Before incorporating in to bases, whitening effect of the licorice extract in terms of tyrosinase inhibitory activity was investigated. Characterizations such as microscopic analysis, pH and viscosity were measured and stability studies such as visual observations in accelerated temperatures, freeze thaw and centrifugation tests were also conducted. Results : Licorice extract showed 81.5% inhibition for anti-tyrosinase assay. According to the microscopic analysis, formulated creams were oil in water emulsions. The pH of the formulations varied with the temperature and creams showed higher stability at lower temperature (at 8°C). Viscosities of the creams of F2 containing high virgin coconut oil ratio were greater than the creams of F1 having lower virgin coconut oil content. According to accelerated stability studies all the cream bases of F1 and F2 were stable at 8°C compared to room temperature. Conclusion : Methanolic extract of licorise can be incorporated with virgin coconut oil, water and Tween 80 to formulate a cream, which is in oil in water nature. Out of the creams that were kept in accelerated temperatures, the creams that were kept in 8 o C were more stable in both the formulations but further improvements are needed to improve the shelf-life of the emulsions.